Fabrication method of package structure having MEMS element

ABSTRACT

A fabrication method of a package structure having at least an MEMS element is provided, including: preparing a wafer having electrical connection pads and the at least an MEMS element; disposing lids for covering the at least an MEMS element, the lids having a metal layer formed thereon; electrically connecting the electrical connection pads and the metal layer with bonding wires; forming an encapsulant for covering the lids, bonding wires, electrical connection pads and metal layer; removing portions of the encapsulant to separate the bonding wires each into first and second sub-bonding wires, wherein top ends of the first and second sub-bonding wires are exposed, the first sub-bonding wires electrically connecting to the electrical connection pads, and the second sub-bonding wires electrically connecting to the metal layer; forming metallic traces on the encapsulant for electrically connecting to the first sub-bonding wires; forming bumps on the metallic traces; and performing a singulation process.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims under 35 U.S.C. §119(a) the benefit of TaiwaneseApplication No. 099101443 filed Jan. 20, 2010 the entire contents ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fabrication methods of packagestructures, and more particularly, to a fabrication method of a packagestructure having a MEMS (Micro Electro Mechanical System) element.

2. Description of Related Art

MEMS (Micro Electro Mechanical System) techniques integrate electricaland mechanical functions into a single element using microfabricationtechnology. A MEMS element is disposed on a chip and covered by a shieldor packaged with an underfill adhesive so as to form a MEMS packagestructure. FIGS. 1A to 1F are cross-sectional views of conventionalfabrication methods of different package structures with a MEMS element.

FIG. 1A shows a package structure disclosed by U.S. Pat. No. 6,809,412.Referring to FIG. 1A, the package structure comprises a substrate 10, achip 14 disposed on the substrate 10 and having a MEMS element 141, aplurality of bonding wires 11 electrically connecting the substrate 10and the chip 14, and a lid 12 disposed on the substrate 10 to cover thechip 14, the MEMS element 141 and the bonding wires 11.

FIG. 1B shows a package structure disclosed by U.S. Pat. No. 6,303,986.Referring to FIG. 1B, the package structure comprises a lead frame 10′,a chip 14 disposed on the lead frame 10′ and having a MEMS element 141,a lid 12 disposed on the chip 14 for covering the MEMS element 141, aplurality of bonding wires 11 electrically connecting the lead frame 10′and the chip 14, and a packaging material 15 covering the lead frame10′, the bonding wires 11, the lid 12 and the chip 14.

However, the use of the carriers (the substrate 10 of FIG. 1A and thelead frame 10′ of FIG. 1B) increases the thickness of the overallstructures and cannot meet the demand for miniaturization. Accordingly,package structures without a carrier are developed, as shown in FIGS. 1Cto 1D.

FIG. 1C shows a package structure disclosed by U.S. Pat. No. 7,368,808.Referring to FIG. 1C, the package structure comprises: a chip 14 withelectrical connection pads 140; a MEMS element 141 disposed on the chip14; and a lid 12 disposed to cover the MEMS element 141, wherein aplurality of conductive through holes 120 is formed in the lid 12, and aplurality of contact pads 122 are disposed at the two sides of theconductive through holes 120, such that the contact pads 122 located atthe inner sides of the lid 12 are electrically connected to theelectrical connection pads 140 of the chip 14, respectively. Further, aplurality of solder balls 16 is formed on the contact pads 122 locatedat the outer sides of the lid 12 for electrically connecting the chip 14to another electronic element.

FIG. 1D shows a package structure disclosed by U.S. Pat. No. 6,846,725.Referring to FIG. 1D, the package structure comprises: a chip 14 withelectrical connection pads 140; a MEMS element 141 disposed on the chip14; and a lid 12 disposed to cover the MEMS element 141, wherein aplurality of solder bumps 142 is formed on the electrical connectionpads 140, a plurality of conductive through holes 120 is formed in thelid 12 and a plurality of contact pads 122 are disposed at the two sidesof the conductive through holes 120, respectively, and the contact pads122 located at the inner sides of the lid 12 are electrically connectedto the solder bumps 142, and the contact pads 122 located at the outersides of the lid 12 are used for electrically connecting the chip 14 toanother electronic element.

The above structures dispense with a carrier and meet the demand forminiaturization. However, forming the conductive through holes 120 inthe lid 12 by drilling incurs high costs. In addition, misalignment orunstable connection can easily occur to the contact pads 122 which flankthe conductive through holes 120, thus leading to poor electricalconnection and further adversely affecting the electrical connectionquality between the chip 14 and the external electronic element.Accordingly, a package structure dispensing with conductive throughholes is provided, as shown in FIG. 1E.

FIG. 1E shows a package structure disclosed by U.S. Pat. No. 6,828,674.Referring to FIG. 1E, the package structure comprises: a chip 14 withelectrical connection pads 140; a MEMS element 141 disposed on the chip14; a lid 12 with traces 121 at an outer side thereof; a support 13attached to the chip 14 for supporting the lid 12; a plurality ofbonding wires 11 electrically connecting the traces 121 and theelectrical connection pads 140; and a packaging material 15encapsulating the bonding wires 11, the lid 12 and the chip 14, whereinthe packaging material 15 has an opening 150 for exposing a portion ofthe traces 121 such that solder balls 16 are formed on the exposedportion of the traces 121 so as to electrically connect to anotherelectronic device.

However, the above package structure requires a lithography process forforming the traces on the lid, thus incurring high costs. In addition,the solder balls 16 are confined to the vicinity of the lid to therebycause solder ball bridge, limit the signal input/output density of thepackage structure and reduction of the trace, add to the difficulty inattaching the package structure to a circuit board. As such, theapplication field of the package structure is limited. In addition,corresponding to the package structure, a fine pitch circuit board isrequired, thus increasing the cost. Further, such a package structurecannot achieve an EMI shielding effect.

Therefore, it is imperative to overcome the above drawbacks of the priorart.

SUMMARY OF THE INVENTION

In view of the above drawbacks of the prior art, the present inventionprovides a fabrication method of a package structure having at least anMEMS element, which comprises: preparing a wafer having a plurality ofelectrical connection pads and the at least an MEMS element; disposing aplurality of lids on the wafer for covering the at least an MEMSelement, respectively, wherein each of the lids has a metal layer formedthereon; electrically connecting the electrical connection pads and themetal layer with a plurality of bonding wires; forming an encapsulant onthe wafer for covering the lids, the bonding wires, the electricalconnection pads and the metal layer; removing a portion of theencapsulant so as to separate each of the bonding wires into a firstsub-bonding wire and a second sub-bonding wire, wherein the top ends ofthe first sub-bonding wire and the second sub-bonding wire are exposedfrom the top surface of the encapsulant, the first sub-bonding wireselectrically connect to the electrical connection pads and the secondsub-bonding wires electrically connect to the metal layer; forming aplurality of metallic traces on the encapsulant and electricallyconnecting to the first sub-bonding wires, respectively; forming aplurality of bumps on the metallic traces, respectively; and performinga singulation process to obtain a plurality of package structures eachhaving a MEMS element.

In another embodiment, the metallic traces are electrically connected tothe second sub-bonding wires, respectively.

The present invention discloses another fabrication method of a packagestructure having at least a MEMS element, which comprises: preparing awafer having a plurality of electrical connection pads and the at leastan MEMS element; disposing a plurality of lids on the wafer for coveringthe at least an MEMS element, respectively, wherein each of the lids hasa metal layer formed thereon; electrically connecting the electricalconnection pads and the metal layer with a plurality of bonding wires;forming an encapsulant on the wafer for covering the lids, the bondingwires, the electrical connection pads and the metal layer; removing aportion of the encapsulant and a portion of the bonding wires such thatthe top surface of the encapsulant is flush with the top surfaces of thelids, each of the bonding wires has a first sub-bonding wire remainedfor electrically connecting to the corresponding electrical connectionpad, and the top ends of the first sub-bonding wires are exposed fromthe top surface of the encapsulant; forming a plurality of metallictraces on the encapsulant and electrically connecting to the firstsub-bonding wires, respectively; forming a plurality of bumps on themetallic traces, respectively; and performing a singulation process toobtain a plurality of package structures each having a MEMS element.

The present invention further discloses a fabrication method of apackage structure having at least a MEMS element, which comprises:preparing a wafer having a plurality of electrical connection pads andthe at least an MEMS element; disposing a plurality of lids on the waferfor covering the at least an MEMS element, respectively, wherein each ofthe lids has a metal layer formed thereon; electrically connecting theelectrical connection pads and the metal layer with a plurality ofbonding wires; forming an encapsulant on the wafer for covering thelids, the bonding wires, the electrical connection pads and the metallayer; removing a portion of the encapsulant so as to separate each ofthe bonding wires into a first sub-bonding wire and a second sub-bondingwire, wherein the top ends of the first sub-bonding wires and the secondsub-bonding wires are exposed from the top surface of the encapsulant,the first sub-bonding wires electrically connect to the electricalconnection pads, and the second sub-bonding wires electrically connectto the metal layer; forming a plurality of metallic traces on theencapsulant and each composed of a first sub-metallic trace and a secondsub-metallic trace, wherein the first sub-metallic traces electricallyconnect to the first sub-bonding wires, and the second sub-metallictraces electrically connect to the second sub-bonding wires; forming aplurality of bumps on the metallic traces, respectively; and performinga singulation process to obtain a plurality of package structures eachhaving a MEMS element.

With the fabrication method of the present invention, thethus-fabricated package structure having a MEMS element is formeddirectly on a wafer without the need of a carrier, thus reducing thethickness of the overall structure. The present invention also dispenseswith a drilling process for forming openings in the lid so as tosimplify the fabrication process and reduce the fabrication cost.Further, the position of the bumps is not limited to the top of the lid.Instead, the bumps are disposed at any positions of the top surface ofthe package structure. Furthermore, the fabrication process is directlyperformed on a wafer instead of on a conventional package with acarrier, thereby eliminating the need of singulating the wafer andadhering the singulated chip to a carrier as in the prior art andgreatly saving time and costs. In addition, the lid is connected to aground end through the sub-bonding wires and the metallic traces so asto achieve an EMI shielding effect.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1E are cross-sectional views of a conventional fabricationmethod of package structures having a MEMS element;

FIGS. 2A to 2F are cross-sectional views of a fabrication method of apackage structure having a MEMS element according to a first embodimentof the present invention, wherein FIGS. 2E′ and 2E″ are partiallyenlarged views of other embodiments of the fabrication method;

FIG. 3 is a cross-sectional view of a fabrication method of a packagestructure having a MEMS element according to a second embodiment of thepresent invention;

FIG. 4 is a cross-sectional view of a fabrication method of a packagestructure having a MEMS element according to a third embodiment of thepresent invention;

FIG. 5 is a cross-sectional view of a fabrication method of a packagestructure having a MEMS element according to a fourth embodiment of thepresent invention;

FIG. 6 is a cross-sectional view of a fabrication method of a packagestructure having a MEMS element according to a fifth embodiment of thepresent invention; and

FIG. 7 is a cross-sectional view of a fabrication method of a packagestructure having a MEMS element according to a sixth embodiment of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following illustrative embodiments are provided to illustrate thedisclosure of the present invention, these and other advantages andeffects can be apparent to those in the art after reading thisspecification.

First Embodiment

FIGS. 2A to 2F are cross-sectional views of a fabrication method of apackage structure having a MEMS element according to a first embodimentof the present invention.

Referring to FIG. 2A, a wafer 20 is prepared, which has a plurality ofelectrical connection pads 201 and a plurality of MEMS elements 202. Itshould be noted that only a portion of the wafer is shown in FIG. 2A.

Referring to FIG. 2B, a plurality of lids 21 is disposed on the wafer 20for covering the MEMS elements 202, respectively. The wafer 20 is madeof silicon. The MEMS elements 202 are gyroscopes, accelerometers or RFMEMS elements. The lids 21 are made of a conductive material or anon-conductive material such as glass, silicon, metal or ceramic. Ametal layer 211 or a plurality of bonding pads, as shown in FIG. 2B′, isfurther formed on each of the lids 21 by such as sputtering, which aremade of Al, Cu, Au, Pd, Ni/Au, Ni/Pd, TiW/Au, Ti/Al, TiW/Al, Ti/Cu/Ni/Auor a combination thereof. After the formation of the metal layer 211 oneach of the lids 21, cavities are formed on the other side of each ofthe lids 21, such that the cavities thus formed are opposite to themetal layer 211.

Referring to FIG. 2C, a plurality of bonding wires 22 is formed toelectrically connect the electrical connection pads 201 and the metallayer 211, and an encapsulant 23 is formed on the wafer 20 to cover thelids 21, the bonding wires 22, the electrical connection pads 201 andthe metal layer 211. Therein, the encapsulant 23 is made of a dielectricadhesive material such as a thermo-setting resin or silicone, whereinthe thermo-setting resin is, for example, an epoxy resin, an epoxymolding compound (EMC) or polyimide.

Referring to FIG. 2D, a portion of the encapsulant 23 is removed, thatis, the upper portion of the encapsulant 23 and the top portions of wireloops of the bonding wires 22 are removed such that each of the bondingwires 22 is divided into a first sub-bonding wire 221 and a secondsub-bonding wire 222 which are separate from each other. The top ends ofthe first sub-bonding wires 221 and the second sub-bonding wires 222 areexposed from the top surface of the encapsulant 23. The firstsub-bonding wires 221 are electrically connected to the electricalconnection pads 201. The second sub-bonding wires 222 are electricallyconnected to the metal layer 211. The upper portion of the encapsulant23 is removed by grinding, laser, plasma, chemical etching, or chemicalmechanical polishing (CMP.)

Referring to FIG. 2E, a plurality of metallic traces 24 is formed on theencapsulant 23 to electrically connect to the first sub-bonding wires221, respectively, and electrically isolate the second sub-bonding wires222. In addition, one end of each of the metallic traces 24 isconfigured to extend towards the corresponding MEMS element 202 or theperiphery of the MEMS element 202 (not shown.) The layout of themetallic traces 24 is flexibly adjusted according to the electricaldemands and layout density limit. Furthermore, bumps 25 are formed onthe metallic traces 24. For example, the bumps 25 are formed on the endsof the metallic traces 24. The bumps 25 are made of metal or alloy, andhave soldering characteristics. The bumps 25 are preferably made ofSn/Pd, Sn/Ag/Cu or Au. Referring to FIG. 2E′, prior to formation of thebumps 25, a first insulation layer 240 a is formed on the encapsulant 23and the metallic traces 24. The first insulation layer 240 a has aplurality of openings 2401 for exposing the metallic traces 24. Thebumps 25 are formed at the openings 2401 for electrically connecting tothe metallic traces 24. In addition, prior to formation of the metallictraces 24, a second insulation layer 240 b is formed on the encapsulant23. The second insulation layer 240 b has a plurality of openings 2402for exposing the first sub-bonding wires 221 and electrically isolatingthe second sub-bonding wires 222. The structure shown in FIG. 2E′ isachieved through redistribution layer (RDL) technique.

An insulation layer (not shown) such as green paint, is formed beforethe bumps 25 are formed. The insulation layer has a plurality ofopenings for exposing the metallic traces 24 such that the bumps 25 areelectrically connected to the exposed metallic traces 24.

In another embodiment as shown in FIG. 2E″, the second insulation layer240 b has a plurality of openings 2402 for exposing the secondsub-bonding wires 222 and electrically isolating the first sub-bondingwires 221, and the metallic traces 24 electrically connect to the secondsub-bonding wires 222. A first insulation layer 240 a is formed on theencapsulant 23 and the metallic traces 24 and has a plurality ofopenings 2401 for exposing the metallic traces 24, and the bumps 25 areformed at the openings 2401 for electrically connecting to the metallictraces 24. The layout of the metallic traces 24 is designed to stay awayfrom the top of the second sub-bonding wires 222 to achieve anelectrical isolation effect (not shown.)

Furthermore, an under bump metal layer 26 is formed at the openings 2401of the first insulation layer 240 a before the bumps 25 are formed.

Referring to FIG. 2F, a singulation process is performed to obtain aplurality of package structures 2 each having a MEMS element 202.

The present invention further discloses a package structure 2 having aMEMS element, which comprises: a chip 20′ having a plurality ofelectrical connection pads 201 and at least a MEMS element 202; a lid 21disposed on the chip 20′ for covering the MEMS element 202 and having ametal layer 211 formed thereon; a plurality of first sub-bonding wires221 electrically connecting to the electrical connection pads 201; aplurality of second sub-bonding wires 222 electrically connecting to themetal layer 211; an encapsulant 23 disposed on the chip 20′ and coveringthe lid 21, the first sub-bonding wires 221 and the second sub-bondingwires 222, wherein the top ends of the first sub-bonding wires 221 andthe second sub-bonding wires 222 are exposed from the top surface of theencapsulant 23; and a plurality of metallic traces 24 disposed on theencapsulant 23 and electrically connecting to the first sub-bondingwires 221.

In another embodiment, as shown in FIG. 2E″, the metallic traces 24 aredisposed on the encapsulant 23 and electrically connecting to the secondsub-bonding wires 222. In a preferred embodiment, the packagingstructure 2 further comprises a first insulation layer 240 a formed onthe encapsulant 23 and the metallic traces 24 and having a plurality ofopenings 2401 for exposing the metallic traces 24, and a plurality ofbumps 25 is formed at the openings 2401 for electrically connecting tothe metallic traces 24. The packaging structure 2 further comprises asecond insulation layer 240 b formed on the encapsulant 23 and havingopenings 2402 for exposing the first sub-bonding wires 221 or the secondsub-bonding wires 222 such that the metallic traces 24 are formed in theopenings 2402 and on the second insulation layer 240 b.

In the embodiment where the first insulation layer 240 a is formed, thepackage structure 2 further comprises an under bump metal layer 26formed between the bumps 25 and the first insulation layer 240 a.

In the package structure 2 having a MEMS element of the presentinvention, each of the metallic traces 24 has one end extending towardsthe corresponding MEMS element 202 and having a bump 25 formed thereon.To be specific, the metallic traces 24 essentially extend from theelectrical connection pads 201 to the MEMS elements 202.

In the package structure 2, the chip 20′ is made of silicon. The MEMSelement 202 is a gyroscope, an accelerometer or a RF MEMS element. Thelid 21 is made of a conductive material or a non-conductive materialsuch as metal, silicon, glass or ceramic. The metal layer 211 is made ofAl, Cu, Au, Pd, Ni/Au, Ni/Pb, TiW/Au, Ti/Al, TiW/Al, Ti/Cu/Ni or acombination thereof. The package layer 23 is made of a dielectricadhesive material such as a thermo-setting resin or silicone. Thethermo-setting resin is, for example, an epoxy resin, an epoxy moldingcompound (EMC) or polyimide.

In the case the metallic traces electrically isolate the secondsub-bonding wires, one end of each of the metallic traces 24 extendstowards the MEMS element 202 and even extends to the lid. At a positionwhere the bottom of the metallic traces 24 is adjacent to the secondsub-bonding wires 222, an insulation pad made of the same material asthe second insulation layer 240 b is formed for electrically isolatingthe second sub-bonding wires 222. Similarly, in the case the metallictraces electrically isolate the first sub-bonding wires, an insulationpad is disposed at a position where the bottom of the metallic traces 24is adjacent to the first sub-bonding wires 221.

In the package structure 2, the electrical connection pads 201 arelocated at the outer periphery of the lid 21.

In the package structure 2, the bumps 25 are made of metal or alloy andhaving soldering characteristics. The bumps 25 are preferably made ofSn/Pb, Sn/Ag or Au.

Second Embodiment

FIG. 3 is a cross-sectional view of a fabrication method of a packagestructure 3 having a MEMS element according to a second embodiment ofthe present invention. The package structure 3 of FIG. 3 is similar tothe package structure 2 of FIG. 2F, but the main difference therebetweenis that the metal layer 211 of the package structure 3 is composed of aplurality of bonding pads, and the metallic traces 24 electricallyconnect to the first sub-bonding wires 221 and the second sub-bondingwires 222, respectively. The fabrication method of the package structure3 is similar to the first embodiment, and the first insulation layer 240a and the second insulation layer 240 b are formed in the same way asshown in FIGS. 2E′ and FIG. 2E″; hence, detailed description of thefabrication method of the package structure 3 is omitted herein.

Third Embodiment

FIG. 4 is a cross-sectional view of a fabrication method of a packagestructure 4 having a MEMS element according to a third embodiment of thepresent invention. The package structure 4 in the third embodiment issimilar to the package structure 2 of FIG. 2F, but a main differencetherebetween is that the top surface of the encapsulant 23 of thepackage structure 4 is flush with the top surface of the lid 21, i.e.,the metal layer 211 is exposed from the encapsulant 23, and the secondsub-bonding wires 222 are removed at the time a portion of theencapsulant 23 is removed. As such, the first sub-bonding wires 221 areremained for electrically connecting to the electrical connection pads201, and the top ends of the first sub-bonding wires 221 are exposedfrom the top surface of the encapsulant 23. The fabrication method ofthe package structure 4 is similar to the first embodiment, and thefirst insulation layer 240 a and the second insulation layer 240 b areformed in the same way as shown in FIGS. 2E′ and 2E″; hence, detaileddescription of the fabrication method of the package structure 4 isomitted herein.

Fourth Embodiment

FIG. 5 is a cross-sectional view of a fabrication method of a packagestructure 5 having a MEMS element according to a fourth embodiment ofthe present invention. The package structure 5 in the fourth embodimentis similar to the package structure 4 in FIG. 4, but a big differencetherebetween is that the metal layer 211 of the package structure 5 isremoved at the time a portion of the encapsulant 23 is removed, and themetallic traces 24 extend to the lid 21. The fabrication method of thepackage structure 5 is similar to the third embodiment, and the firstinsulation layer 240 a and the second insulation layer 240 b are formedin the same way as shown in FIGS. 2E′ and 2E″; hence, detaileddescription of the fabrication method of the package structure 5 isomitted herein.

Fifth Embodiment

FIG. 6 is a cross-sectional view of a fabrication method of a packagestructure 6 having a MEMS element according to a fifth embodiment of thepresent invention. The package structure 6 in the fifth embodiment issimilar to the package structure 5 in FIG. 5, but the main differencetherebetween is that the metallic traces 24 extend on the lid 21. Thefabrication method of the package structure 6 is similar to the firstembodiment; hence, detailed description of the fabrication method of thepackage structure 6 is omitted herein.

Sixth Embodiment

FIG. 7 is a cross-sectional view of a fabrication method of a packagestructure 7 having a MEMS element according to a sixth embodiment of thepresent invention. The package structure 7 in the sixth embodiment issimilar to the package structure 2 of FIG. 2F, but the main differencestherebetween include: the metallic traces 24 of the package structure 7in the sixth embodiment are separated into first sub-metallic traces 241electrically connecting to the first sub-bonding wire 221 and secondsub-metallic traces 242 electrically connecting to the secondsub-bonding wire 222; each of the first sub-metallic traces 241 has oneend extending towards the periphery of the chip 20′ and having a bump251 formed thereon; and each of the second sub-metallic traces 242 hasone end extending towards the periphery of the MEMS element 202 andhaving a bump 252 formed thereon. Since the fabrication method of thepackage structure 7 is similar to the first embodiment, detaileddescription of the fabrication method of the package structure 7 isomitted herein.

Referring to FIG. 2E′ again, the package structure 7 further comprises afirst insulation layer formed on the encapsulant and the metallic tracesand having a plurality of openings for exposing the metallic traces. Thepackage structure 7 further comprises a second insulation layer (notshown) formed on the encapsulant and having a plurality of openings forexposing the first and second sub-bonding wires such that the metallictraces are formed in the openings and on the second insulation layer.

In the package structure 7, the second sub-bonding wires 222, the secondsub-metallic traces 242 and the bumps 252 are grounded for achieving anEMI shielding effect.

According to the present invention, the package structure having a MEMSelement is formed directly on a wafer without the need of a carrier,thus reducing the thickness of the overall structure. The presentinvention also dispenses with a drilling process for forming openings inthe lid so as to simplify the fabrication process and reduce thefabrication cost. Further, the position of the bumps is not limited tothe top of the lid. Instead, the bumps are disposed at any positions ofthe top surface of the package structure. Furthermore, the fabricationprocess is directly performed on a wafer instead of on a conventionalpackage with a carrier, thereby eliminating the need of singulating thewafer and adhering the singulated chip to a carrier as in the prior artand greatly saving time and cost. In addition, the lid is connected to aground end through the sub-bonding wires and the metallic traces so asto achieve an EMI shielding effect.

The above-described descriptions of the detailed embodiments areintended to illustrate the preferred implementation according to thepresent invention but are not intended to limit the scope of the presentinvention, Accordingly, all modifications and variations completed bythose with ordinary skill in the art should fall within the scope ofpresent invention defined by the appended claims.

What is claimed is:
 1. A fabrication method of a package structurehaving at least a Micro Electro Mechanical System (MEMS) element,comprising the steps of: preparing a wafer having a plurality ofelectrical connection pads and the at least an MEMS element; disposing aplurality of lids on the wafer for covering the at least an MEMSelement, respectively, wherein each of the lids has a metal layer formedthereon; electrically connecting the electrical connection pads and themetal layer with a plurality of bonding wires; forming an encapsulant onthe wafer for covering the lids, the bonding wires, the electricalconnection pads and the metal layer; removing a portion of theencapsulant so as to separate each of the bonding wires into a firstsub-bonding wire and a second sub-bonding wire, wherein top ends of thefirst sub-bonding wire and the second sub-bonding wire are exposed froma top surface of the encapsulant, the first sub-bonding wireselectrically connecting to the electrical connection pads, and thesecond sub-bonding wires electrically connecting to the metal layer;forming a plurality of metallic traces on the encapsulant forelectrically connecting to the first sub-bonding wires, respectively;forming a plurality of bumps on the metallic traces, respectively; andperforming a singulation process to obtain a plurality of packagestructures each having the at least an MEMS element.
 2. The method ofclaim 1, wherein the electrical connection pads are disposed at an outerperiphery of the lids.
 3. The method of claim 1, further comprisingforming a first insulation layer on the encapsulant and the metallictraces before forming the bumps, wherein the first insulation layer hasa plurality of openings for exposing the metallic traces such that thebumps are formed at the openings for electrically connecting to themetallic traces.
 4. The method of claim 1, further comprising forming asecond insulation layer on the encapsulant before forming the metallictraces, wherein the second insulation layer has a plurality of openingsfor exposing the first sub-bonding wires.
 5. The method of claim 1,wherein each of the metallic traces has an end extending towards thecorresponding MEMS element and having the corresponding bump formedthereon.
 6. The method of claim 1, wherein the metal layer is composedof a plurality of bonding pads.
 7. The method of claim 1, wherein themetal layer is formed by sputtering or evaporation.
 8. The method ofclaim 1, wherein the portion of the encapsulant is removed by grinding.9. The method of claim 1, wherein the metallic traces furtherelectrically connect to the second sub-bonding wires.